Thyroxine, Total is a topic covered in the Davis's Lab & Diagnostic Tests.

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Common Use:
A complementary laboratory test in evaluating thyroid hormone levels, a screening test for newborns to detect thyroid dysfunction, and a tool to evaluate the effectiveness of therapeutic thyroid therapy.

Serum collected in a gold-, red-, or red/gray-top tube. Plasma collected in a green-top (heparin) tube is also acceptable.

Normal Findings:
(Method: Immunoassay)

AgeConventional UnitsSI Units (Conventional Units × 12.9)
Cord blood6.6–17.5 mcg/dL85–226 nmol/L
1–30 d5.4–22.6 mcg/dL70–292 nmol/L
1 mo–23 mo5.4–16.6 mcg/dL70–214 nmol/L
2–6 yr5.3–15 mcg/dL68–194 nmol/L
7–11 yr5.7–14.1 mcg/dL74–182 nmol/L
12–19 yr4.7–14.6 mcg/dL61–188 nmol/L
Adult4.6–12 mcg/dL59–155 nmol/L
 Pregnant female5.5–16 mcg/dL71–206 nmol/L
Over 60 yr5–10.7 mcg/dL64–138 nmol/L

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